1. Field of the Invention
The present invention relates to a cantilever unit for use in the atomic probe microscope and the like.
2. Description of the Related Art
The scanning tunneling microscope (STM) invented by Binning et al (G. Binning, H. Rohrer and E. Weibel: Surface Studies by Scanning Tunneling Microscope. Phys. Rev. Lett., 49 (1982) 57) has been more and more widely used in various fields as a microscope capable of viewing the unevenness of sample surface in the order of atoms.
A typical arrangement of the STM includes a probe and a system for scanning the probe in directions X and Y wherein tunnel current flowing between the probe and a sample is detected, while scanning the probe in the directions X and Y, to form the two-dimensional image of the sample.
However, the STM is designed to detect the tunnel current. Therefore, samples which can be viewed by the STM are limited to conductive ones, thereby making it impossible to view insulation materials through the STM.
The Japanese Patent Disclosure Sho 62-130302 discloses an atomic force microscope (AFM) capable of viewing insulation samples with an accuracy of atomic order.
The arrangement of the AFM is similar to that of the STM. When a cantilever provided with a sharp projection (or first probe) at the tip thereof is opposed to and located near a sample, interaction is created between atoms in the tip of the probe and those in the sample. When the positional relation of the probe and the sample is changed in the directions X and Y, the cantilever is displaced corresponding to the unevenness of the sample surface. This displacement of the cantilever is measured by a second STM system provided with a second probe which is arranged above the cantilever. Insulation materials which could not be viewed by the STM can be thus indirectly measured.
Further, T. R. Albrecht et al reported on a micro-cantilever for use with the AFM which was made using the anisotropic etching of silicon (T. R. Albrecht and C. F. Quate: Atomic Resolution Imaging of a Nonconductor by Atomic Force Microscope. J. Appl. Phys., 62 (1987) 2599). The process of manufacturing semiconductor ICs is used to make this micro-cantilever. The cantilever thus made can therefore have a high accuracy of micron millimeter order and an extremely excellent reproductiveness.
In the case of the atomic probe microscopes such as the STM and the AFM, the probe is located extremely close to the sample. This sometimes causes the probe to be contacted with the sample, so that the probe can be deformed or the lever section for supporting the probe can be broken. Therefore, these microscopes must be used while exchanging the cantilever with a new one every time the above-mentioned problem is caused. In order to obtain data with excellent reproductiveness by using the new cantilever, it is important that the shape of the exchanged micro-cantilever corresponds to that of the cantilever perviously used.
Further, the accuracy of data measured by the AFM depends upon how accurately the micro-cantilever is positioned relative to the cantilever displacement measuring system which is supported on the body of the AFM as well as the accuracy of the exchanged micro-cantilever itself. When AFM is used, considering the necessity of exchanging the cantilever with a new one, therefore, the S/N of an image formed by the AFM is determined by how accurately the new micro-cantilever is attached to its original position.
It is important in atomic probe microscopes that the exchange of the micro-cantilever with new ones can be made simple and that the new micro-cantilever can be attached to its original position with high reproductiveness. This also determines whether or not the atomic probe microscopes can be easily used.
However, no means for easily and accurately attaching the micro-cantilever to its original position has been provided yet.